The idea that formative assessments embedded in a curriculum could help guide teachers toward better instructional practices that lead to greater student learning has taken center stage in science assessment research. In order to embed formative assessments in a curriculum, curriculum developers and assessment specialists should collaborate to create these assessment tasks. This article describes the development of the formal embedded formative assessments and implementation plans for the collaborative research study. It describes the fundamental shift away from "summative assessment scripts" to formative assessments lesson scripts. Assessment tasks and implementation plans are described along with the rationale for why these tasks were selected and where these tasks were placed in the curriculum. Finally, we conclude about how to embed formative assessments in new or existing curricula and how to help teachers use these assessments successfully. We point out the critical importance of collaboration and professional development aimed at enabling teachers to re-conceptualize the role of assessments in their teaching, linking formative assessments to overall goals, and providing a learning trajectory as reference for teachers to locate students' ideas in the trajectory and provide feedback accordingly. (Contains 8 figures and 1 footnote.)